Notebook computer has become more and more popular because it can be conveniently normally operated without external power supply. In order to let a notebook computer work longer with self-provided power supply, the hardware circuit of the keyboard therein must be designed with low consumption of power supply. According to conventional method CMOS (Complimentary Metaloxide Semiconductor) is commonly used to replace NMOS (N-channel Metal Oxide Semiconductor) so as to reduce the consumption of electric current. Some manufacturers may adopt QFT Type single chip packing method. However, the basic hardware structure and firmware design of a notebook computer generally remain unchanged relative to a standard computer keyboard design. The present invention not only adopts CMOS and QFP Type but also applies the functions of Idle Mode and Power Down of the CMOS used. By means of firmware processing to match with a special hardware design, keyboard and CMOS almost consume zero electric current when there is no any key code made or no any command from the mainframe (because they are kept in idle mode or power down mode). In comparing the consumption of electric current in CMOS under Idle Mode and Power Down to its normal working mode, the former is about 15% or less relative to the normal working mode. In some single chips, the consumption of electric current under Power Down may be as low as 10 .mu.A. It has been apparent that an operator who uses a keyboard expends much time in idle condition without touching a key than in pressing keys (the so-called "idle condition" includes the dead time between each two code making actions while an user is spending time in thinking, and any dead time caused by any reasons), that is to say, idle time in much longer than execution time. The present invention is to make use of this phenomenon of the distribution of time permitting a keyboard to enter a power-saving mode during idle time, so as to reduce power consumption.
In regular single chip microcomputers, when a firmware is set to wake up from Idle Mode or Power Down, an external interrupt signal or single chip reset should be required.